Rice prices have been hitting record highs
The world's largest retailer, Wal-Mart, is restricting sales of rice at one of its chains - the latest sign of a global shortage of the staple food.
Sam's Club, Wal-Mart's cash-and-carry division, says customers can buy a maximum of four bags per visit.
The limit applies to jasmine, basmati and long grain white rice.
The international price of rice has risen by 68% this year and Wal-Mart said the restrictions were "due to recent supply and demand trends".
There are more than 550 Sam's Club stores in the US.
With food prices rising, customers have been buying basic goods in bulk.
Wal-Mart said it was not restricting the amounts of flour or oil customers can purchase "at this time".
The prices of soybeans, corn and wheat have also soared and are currently near their all-time peaks.
Rice-producing countries like Vietnam and India have curbed exports to keep domestic prices under control and there are fears that Thailand - the world's largest rice exporter - could follow suit.
Rice shortages have sparked protests in several countries including the Philippines, Haiti and Egypt.
Wal-Mart said it was working with suppliers to address the shortage.